1. Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus and a method of manufacturing a semiconductor device.
2. Description of the Related Art
One of methods of molding or forming a resin on the periphery of the wafer of a semiconductor device in process, such as a rectifier element, is disclosed in Japanese Unexamined Patent Publication No. 63- 141370. In order to employ the resultant form of the resin for positioning the assembly in subsequent processes, a semiconductor manufacturing apparatus and a resin molding method has been proposed recently which form a resin on the periphery of a wafer using a die assembly.
Hereinafter a conventional semiconductor manufacturing apparatus and resin molding method for molding resin on the periphery of a wafer using a die assembly will be described. FIG. 1 illustrates a semiconductor device in process, FIG. 2 illustrates a conventional semiconductor manufacturing apparatus, and FIG. 3 illustrates a position alignment gauge for wafer.
The conventional semiconductor manufacturing apparatus, as shown in FIG. 2, is constructed from a molding unit 1, a resin injecting unit 2 and a control unit 4 provided in a frame 3. The molding unit 1 comprises an upper mold 5 and a lower mold 6 which face each other vertically. The die assembly comprised of the upper mold 5 and the lower mold 6 is maintained at a given temperature at the time of molding of resin in order to solidify it.
In such an apparatus, when a wafer 7 is placed on the lower mold 6, the upper mold 5 travels to the lower mold 6 under the control of the control unit 4, thereby closing the die assembly. At this point, a ring-like cavity into which resin is injected is formed between the periphery of the wafer 7 and the lower mold 6. After the closing of the die assembly, the resin injecting unit 2 travels in the direction of the molding unit 1, so that its discharge nozzle 8 hits against the die assembly. Resin is subsequently injected from the discharge nozzle into the ring-like cavity formed within the die assembly through an inlet (not shown) of the die assembly. After the resin has been solidified, the wafer 7 is taken out of the lower mold 6. As a result, a ring-like resin 9 is formed on the periphery of the wafer 7 as shown in FIG. 1.
The resin thus formed is employed as an insulator or a protective film when the wafer 7 is incorporated into a semiconductor device. However, insulation deterioration is liable to occur when the width H from the edge of the wafer 7 to the periphery of the resin 9 is short. If, therefore, misalignment of the center of the wafer 9 with the center of the ring-like resin 9 should occur, a portion of a very small width H would be produced. Namely, it is required to bring the center of the wafer 7 and the center of the ring-like resin 9 in exact alignment with each other.
To this end, such a position alignment gauge 10 as shown in FIG. 3 is used. That is, the position alignment gauge 10 is formed such that it is circle in shape and its outside diameter and inside diameter are equal to the outside diameter of the lower mold 6 and the diameter of the wafer 7, respectively. Thus, when the wafer 7 is loaded into the positioning gauge 10 with the aid of a pincette or the like, the center of the wafer 7 and the center of the gauge 10 are brought in alignment with each other. Here a vacuum chuck 12 having inside diameter equal to the outside diameter of the position alignment gauge 10 is engaged with the gauge 10. After the wafer 7 is attracted to the vacuum chuck 12 by the use of vacuum force, the position alignment gauge 10 is removed. The vacuum chuck 12 is moved onto the lower mold 6 and then engaged with it. Subsequently the operation of the vacuum chuck is stopped with the result that the wafer 7 is placed in position on the lower mold 6. That is, the wafer 7 is consequently placed on the lower mold 6 with their centers aligned with each other.
With the conventional method, as described above, the wafer is treated manually by a worker and taking of the wafer out of the mold after the formation of the resin is also performed manually by the worker. That is, with the conventional method of molding or forming a resin, since the process of placing the wafer on the mold is performed by hand using the vacuum chuck 12, the worker has to be very careful to prevent breakage of the wafer which is liable to occur when it is placed and removed. Thus, this process takes a long time. The position alignment gauge 10, as described above, uses the periphery of the wafer 7 as its reference. Actually even wafers which are considered to be equal to one another in diameter certainly have a tolerance depending on the accuracy of processing. For this reason, even if the position alignment gauge 10 is used, misalignment of the center of the wafer 7 with the center of the lower mold 6 may occur due to the above-mentioned tolerance when the wafer 7 is placed on the lower mold 6. It is thus difficult to secure the accuracy of a resin pattern with respect to the center of the wafer 7 and to control the difference in quality between workers.
The vacuum chuck 12 as shown in FIG. 3 is used for taking the wafer 7 out of the mold after the resin has been formed and the resin used is a material having high adhesive property. For this reason, even if a material which is difficult for the resin to adhere to is used for the upper and lower molds 5 and 6, it is difficult to release the wafer 7 from the mold smoothly by vacuum force only. Furthermore, the work for taking the wafer 7 out of the mold by hand using the vacuum chuck 12 requires a long time and reduces productivity because a worker becomes careful to prevent wafer breakage which is liable to occur in taking out the wafer and moreover the release of the wafer from the mold is difficult. The wafer 7 may be broken due to a mistake made in taking out it, reducing yield. Moreover, forcible taking out of wafer 7 may produce microcracks within the wafer, thus adversely affecting the quality and reliability of a semiconductor device.
There is also another wafer releasing method which pushes up the under surface of wafer 7 mechanically with a pin. This method has a drawback that wafer 7 is liable to break because of a load imposed on the wafer. Being soft, the resin cannot be pushed up with a pin.
As described above, the conventional method has a drawback that the process of placing a wafer on the lower mold requires time. Moreover, there is another drawback that the accuracy of a resin pattern with respect to the center of a wafer is difficult to increase. Furthermore, there is still another drawback that, since a resin used is highly adhesive, a wafer cannot be released from the die assembly smoothly, requiring time and breaking the wafer by mistake. With the method which pushes the under surface of a wafer up with a pin, on the other hand, there is a drawback that the wafer is liable to break because of pushing load imposed on the wafer.